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Sep 22, 2013
09/13

by
V. C. Barbosa

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We discuss general models of resource-sharing computations, with emphasis on the combinatorial structures and concepts that underlie the various deadlock models that have been proposed, the design of algorithms and deadlock-handling policies, and concurrency issues. These structures are mostly graph-theoretic in nature, or partially ordered sets for the establishment of priorities among processes and acquisition orders on resources. We also discuss graph-coloring concepts as they relate to...

Source: http://arxiv.org/abs/cs/0309044v1

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Sep 21, 2013
09/13

by
Gregory Leighton; Denilson Barbosa

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The eXtensible Markup Language (XML) provides a powerful and flexible means of encoding and exchanging data. As it turns out, its main advantage as an encoding format (namely, its requirement that all open and close markup tags are present and properly balanced) yield also one of its main disadvantages: verbosity. XML-conscious compression techniques seek to overcome this drawback. Many of these techniques first separate XML structure from the document content, and then compress each...

Source: http://arxiv.org/abs/0905.4761v1

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Sep 21, 2013
09/13

by
Valmir C. Barbosa

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We study the growth of networks from a set of isolated ground nodes by the addition of one new node per time step and also of a fixed number of directed edges leading from the new node to randomly selected nodes already in the network. A fixed-width time window is used so that, in general, only nodes that entered the network within the latest window may receive new incoming edges. The resulting directed network is acyclic at all times and allows some of the ground nodes, then called sinks, to...

Source: http://arxiv.org/abs/0706.3805v1

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Sep 21, 2013
09/13

by
Valmir C. Barbosa

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Given two subsets A and B of nodes in a directed graph, the conduciveness of the graph from A to B is the ratio representing how many of the edges outgoing from nodes in A are incoming to nodes in B. When the graph's nodes stand for the possible solutions to certain problems of combinatorial optimization, choosing its edges appropriately has been shown to lead to conduciveness properties that provide useful insight into the performance of algorithms to solve those problems. Here we study the...

Source: http://arxiv.org/abs/1204.6181v1

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Sep 20, 2013
09/13

by
G. Dourado Barbosa

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We propose an alternative interpretation for the meaning of noncommutativity of the string-inspired field theories and quantum mechanics. Arguments are presented to show that the noncommutativity generated in the stringy context should be assumed to be only between the particle coordinate observables, and not of the spacetime coordinates. Some implications of this fact for noncomutative field theories and quantum mechanics are discussed. In particular, a consistent interpretation is given for...

Source: http://arxiv.org/abs/hep-th/0301106v3

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Sep 23, 2013
09/13

by
G. D. Barbosa

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We study the implications of a noncommutative geometry of the minisuperspace variables for the FRW universe with a conformally coupled scalar field. The investigation is carried out by means of a comparative study of the universe evolution in four different scenarios: classical commutative, classical noncommutative, quantum commutative, and quantum noncommutative, the last two employing the Bohmian formalism of quantum trajectories. The role of noncommutativity is discussed by drawing a...

Source: http://arxiv.org/abs/hep-th/0408071v2

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Sep 21, 2013
09/13

by
Geraldo A. Barbosa

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Coincidence-structures in the transverse plane of Type-II spontaneous parametric down-conversion carrying orbital angular momentum are obtained. Azimuthal symmetry breaking around the pump beam direction reveals itself on these quantum images. Analytical expressions for the amplitude probability of the down conversion process are shown including the nonlinear polarizability components.

Source: http://arxiv.org/abs/0706.0894v1

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Sep 18, 2013
09/13

by
Geraldo A. Barbosa

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This work shows how two parties A and B can securely share sequences of random bits at optical speeds. A and B possess true-random physical sources and exchange random bits by using a random sequence received to cipher the following one to be sent. A starting shared secret key is used and the method can be described as an unlimited one-time-pad extender. It is demonstrated that the minimum probability of error in signal determination by the eavesdropper can be set arbitrarily close to the pure...

Source: http://arxiv.org/abs/quant-ph/0212033v4

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Sep 18, 2013
09/13

by
Geraldo A. Barbosa

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One-time pad encrypted files can be sent through Internet channels using current Internet protocols. However, the need for renewing shared secret keys make this method unpractical. This work shows how users can use a fast physical random generator based on fluctuations of a light field and the Internet channel to directly boost key renewals. The transmitted signals are deterministic but carries imprinted noise that cannot be eliminated by the attacker. Thus, a one-time pad for Internet can be...

Source: http://arxiv.org/abs/0704.1484v1

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Sep 23, 2013
09/13

by
Aline Mauricio Barbosa

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We study the existence and uniqueness problem of compact minimal vertical graphs in H^n x R, n greater than or equal to 2, over bounded domains in the slice H^n x {0}, with non-connected boundary having a finite number of C^0 hypersufaces homeomorphic to the sphere S^{n-1}, with prescribed bounded continuous boundary data, under hypotheses relating those data and the geometry of the boundary. We show the nonexistence of compact minimal vertical graphs in H^n x R having the boundary in two...

Source: http://arxiv.org/abs/1303.3089v2

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Sep 17, 2013
09/13

by
Valmir C. Barbosa

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We introduce the notion of a network's conduciveness, a probabilistically interpretable measure of how the network's structure allows it to be conducive to roaming agents, in certain conditions, from one portion of the network to another. We exemplify its use through an application to the two problems in combinatorial optimization that, given an undirected graph, ask that its so-called chromatic and independence numbers be found. Though NP-hard, when solved on sequences of expanding random...

Source: http://arxiv.org/abs/1003.1412v1

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Sep 20, 2013
09/13

by
Geraldo A. Barbosa

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This work shows how a secure Internet for users A and B can be implemented through a fast key distribution system that uses physical noise to encrypt information transmitted in deterministic form. Starting from a shared secret random sequence between them, long sequences of fresh random bits can be shared in a secure way and not involving a third party. The shared decrypted random bits -encrypted by noise at the source- are subsequently utilized for one-time-pad data encryption. The physical...

Source: http://arxiv.org/abs/quant-ph/0607093v2

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Sep 22, 2013
09/13

by
V. C. Barbosa

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For $k\ge 1$, we consider interleaved $k$-tuple colorings of the nodes of a graph, that is, assignments of $k$ distinct natural numbers to each node in such a way that nodes that are connected by an edge receive numbers that are strictly alternating between them with respect to the relation $

Source: http://arxiv.org/abs/math/0309380v1

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Sep 18, 2013
09/13

by
G. D. Barbosa

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We study the conditions for spontaneous symmetry breaking of the (2+1)-dimensional noncommutative phi^6 model in the small-theta limit. In this regime, considering the model as a cutoff theory, it is reasonable to assume translational invariance as a property of the vacuum state and study the conditions for spontaneous symmetry breaking by an effective potential analysis. An investigation of up to the two loop level reveals that noncommutative effects can modify drastically the shape of the...

Source: http://arxiv.org/abs/hep-th/0306064v3

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Jun 27, 2018
06/18

by
FrÃ©dÃ©ric Maffray; Artur Mesquita Barbosa

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A b-coloring of a graph $G$ is a coloring of its vertices such that every color class contains a vertex that has neighbors in all other classes. The b-chromatic number of $G$ is the largest integer $k$ such that $G$ has a b-coloring with $k$ colors. Javadi and Omoomi ("On b-coloring of cartesian product of graphs", Ars Combinatoria 107 (2012) 521-536) proved that the b-chromatic number of $K_n \times K_n$ (the Cartesian product of two complete graphs on $n$ vertices) is in the set...

Topics: Combinatorics, Mathematics

Source: http://arxiv.org/abs/1504.01975

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0.0

Jun 26, 2018
06/18

by
Leonardo S. Barbosa; Nestor Caticha

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We study source localization from high dimensional M/EEG data by extending a multiscale method based on Entropic inference devised to increase the spatial resolution of inverse problems. This method is used to construct informative prior distributions in a manner inspired in the context of fMRI (Amaral et al 2004). We construct a set of renormalized lattices that approximate the cortex region where the source activity is located and address the related problem of defining the relevant variables...

Topics: Quantitative Biology, Neurons and Cognition, Quantitative Methods

Source: http://arxiv.org/abs/1502.03481

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Jul 20, 2013
07/13

by
Andreas Doering; Rui Soares Barbosa

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The so-called topos approach provides a radical reformulation of quantum theory. Structurally, quantum theory in the topos formulation is very similar to classical physics. There is a state object, analogous to the state space of a classical system, and a quantity-value object, generalising the real numbers. Physical quantities are maps from the state object to the quantity-value object -- hence the `values' of physical quantities are not just real numbers in this formalism. Rather, they are...

Source: http://arxiv.org/abs/1107.1083v1

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46

Sep 21, 2013
09/13

by
Ezequiel R. Barbosa; Marcos Montenegro

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We develop a comprehensive study on sharp potential type Riemannian Sobolev inequalities of order 2 by means of a local geometric Sobolev inequality of same kind and suitable De Giorgi-Nash-Moser estimates. In particular we discuss questions like continuous dependence of optimal constants and existence and compactness of extremal maps. The main obstacle arising in the present setting lies at fairly weak conditions of regularity assumed on potential functions.

Source: http://arxiv.org/abs/1011.1037v2

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Sep 22, 2013
09/13

by
Charles H. Lineweaver; Domingos Barbosa

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Recent cosmic microwave background (CMB) measurements over a large range of angular scales have become sensitive enough to provide interesting constraints on cosmological parameters within a restricted class of models. We use the CMB measurements to study inflation-based, cold dark matter (CDM) critical density universes. We explore the 4-dimensional parameter space having as free parameters, Hubble's constant Ho, baryonic fraction Omega_b, the spectral slope of scalar perturbations n and the...

Source: http://arxiv.org/abs/astro-ph/9612146v2

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Jul 20, 2013
07/13

by
Edilson Vargas; Marcia C. Barbosa

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We consider here a blend made of two types of polymers, $A$ and $B$, of different chemical nature. At high temperature the homogeneous mixture is cross-linked. As the temperature is lowered, the two species try to segregate but are kept together by the cross-links. We show that for inhomogeneous, non-regular and non-permanent cross-links, there is a complete segregation at low temperatures if the system is just weakly cross-linked and partial segregation, otherwise. We also demonstrate that...

Source: http://arxiv.org/abs/cond-mat/9712212v1

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Jul 20, 2013
07/13

by
Edilson Vargas; Marcia C. Barbosa

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The phase behavior of a cross-linked polymer blend made of two incompatible species, $A$ and $B$, of different chemical nature is analyzed. Besides a homogeneous phase, this system also exhibits two microphases and a phase of total segregation. The transition between the homogeneous and the microphase is continuous along a $\lambda$-line; a first-order phase boundaries separate the microphase and the disordered phase from the phase of complete segregation. The critical line meets the...

Source: http://arxiv.org/abs/cond-mat/9712211v1

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Sep 23, 2013
09/13

by
Andre Nathan; Valmir C. Barbosa

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An information-theoretic framework known as integrated information theory (IIT) has been introduced recently for the study of the emergence of consciousness in the brain [D. Balduzzi and G. Tononi, PLoS Comput. Biol. 4, e1000091 (2008)]. IIT purports that this phenomenon is to be equated with the generation of information by the brain surpassing the information which the brain's constituents already generate independently of one another. IIT is not fully plausible in its modeling assumptions,...

Source: http://arxiv.org/abs/1012.5649v1

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Jul 20, 2013
07/13

by
R. Aldrovandi; A. L. Barbosa

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The geometrical picture of gauge theories must be enlarged when a gauge potential ceases to behave like a connection, as it does in electroweak interactions. When the gauge group has dimension four, the vector space isomorphism between spacetime and the gauge algebra is realized by a tetrad-like field. The object measuring the deviation from a strict bundle structure has the formal behavior of a spacetime connection, of which the deformed gauge field-strength is the torsion. A generalized...

Source: http://arxiv.org/abs/math-ph/0107021v1

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Sep 20, 2013
09/13

by
R. Aldrovandi; A. L. Barbosa

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Two distinct gauge potentials can have the same field strength, in which case they are said to be ``copies'' of each other. The consequences of this possibility for the general space A of gauge potentials are examined. Any two potentials are connected by a straight line in A, but a straight line going through two copies either contains no other copy or is entirely formed by copies.

Source: http://arxiv.org/abs/math-ph/0410034v1

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25

Sep 22, 2013
09/13

by
Andre Nathan; Valmir C. Barbosa

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When a neuron fires and the resulting action potential travels down its axon toward other neurons' dendrites, the effect on each of those neurons is mediated by the weight of the synapse that separates it from the firing neuron. This weight, in turn, is affected by the postsynaptic neuron's response through a mechanism that is thought to underlie important processes such as learning and memory. Although of difficult quantification, cortical synaptic weights have been found to obey a long-tailed...

Source: http://arxiv.org/abs/0906.3252v1

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Jul 20, 2013
07/13

by
P. P. Avelino; D. Barbosa

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We consider a model for the reionization history of the Universe in which a significant fraction of the observed optical depth is a result of direct reionization by the decay products of a scaling cosmic defect network. We show that such network can make a significant contribution to the reionization history of the Universe even if its energy density is very small (the defect energy density has to be greater than about $10^{-11}$ of the background density). We compute the Cosmic Microwave...

Source: http://arxiv.org/abs/astro-ph/0406063v1

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Sep 21, 2013
09/13

by
Elias Bareinboim; Valmir C. Barbosa

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The load of a node in a network is the total traffic going through it when every node pair sustains a uniform bidirectional traffic between them on shortest paths. We show that nodal load can be expressed in terms of the more elementary notion of a node's descents in breadth-first-search (BFS or shortest-path) trees, and study both the descent and nodal-load distributions in the case of scale-free networks. Our treatment is both semi-analytical (combining a generating-function formalism with...

Source: http://arxiv.org/abs/0712.3924v1

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58

Sep 17, 2013
09/13

by
R. Aldrovandi; A. L. Barbosa

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The cosmological constant Lambda, which has seemingly dominated the primaeval Universe evolution and to which recent data attribute a significant present-time value, is shown to have an algebraic content: it is essentially an eigenvalue of a Casimir invariant of the Lorentz group which acts on every tangent space. This is found in the context of de Sitter spacetimes but, as every spacetime is a 4-manifold with Minkowski tangent spaces, the result suggests the existence of a "skeleton"...

Source: http://arxiv.org/abs/gr-qc/0207044v2

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Sep 19, 2013
09/13

by
Ezequiel R. Barbosa; Marcos Montenegro

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We concerns here with the continuity on the geometry of the second Riemannian L^p-Sobolev best constant B_0(p,g) associated to the AB program. Precisely, for 1

Source: http://arxiv.org/abs/0708.2376v2

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Jun 27, 2018
06/18

by
Ezequiel Barbosa; Ben Sharp; Yong Wei

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Let $(M^{n+1},g,e^{-f}d\mu)$ be a complete smooth metric measure space with $2\leq n\leq 6$ and Bakry-\'{E}mery Ricci curvature bounded below by a positive constant. We prove a smooth compactness theorem for the space of complete embedded $f$-minimal hypersurfaces in $M$ with uniform upper bounds on $f$-index and weighted volume. As a corollary, we obtain a smooth compactness theorem for the space of embedded self-shrinkers in $\mathbb{R}^{n+1}$ with $2\leq n\leq 6$. We also prove some...

Topics: Differential Geometry, Analysis of PDEs, Mathematics

Source: http://arxiv.org/abs/1503.01945

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1.0

Jun 28, 2018
06/18

by
Raul Fuentes-Azcatl; Marcia C. Barbosa

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The model Tip4p/{\epsilon} for water is tested for the presence of thermodynamic and dy- namic anomalies. Molecular dynamic simulations for this model were performed and we show that for this system the density versus temperature at constant pressure ex- hibits a maximum. In addition we also show that the diffusion coefficient versus density at constant temperature has a maximum and a minimum. The anomalous behavior of the density and of the diffusion coefficient obey the water hierachy. The...

Topics: Condensed Matter, Soft Condensed Matter

Source: http://arxiv.org/abs/1508.01972

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10.0

Jun 28, 2018
06/18

by
Raul Fuentes-Azcatl; Marcia C. Barbosa

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A new computational model for Sodium Chloride, the NaCl/{\epsilon}, is proposed. The Force Fields employed here for the description of the NaCl is based on a set of radial particle-particle pair potentials involving Lennard-Jones (LJ) and Coulombic forces. The parameterization is obtained fitting the density of the crystal and the density and the dielectric constant of the mixture of salt with water at diluted solution. Our model shows good agreement with the experimental values for the density...

Topics: Condensed Matter, Soft Condensed Matter

Source: http://arxiv.org/abs/1508.01971

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1.0

Jun 27, 2018
06/18

by
V. S. Barbosa; V. A. Menegatto

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We present a necessary and sufficient condition for the strict positive definiteness of a real, continuous, isotropic and positive definite kernel on a two-point compact homogeneous space. The characterization adds to others previously obtained by D. Chen at all (2003) in the case in which the space is a sphere of dimension at least 2 and Menegatto at all (2006) in the case in which the space is the unit circle. As an application, we use the characterization to improve upon a recent result on...

Topics: Functional Analysis, Mathematics

Source: http://arxiv.org/abs/1505.00591

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Jun 27, 2018
06/18

by
V. S. Barbosa; V. A. Menegatto

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In this paper we study continuous kernels on compact two point homogeneous spaces which are positive definite and zonal (isotropic). Such kernels were characterized by R. Gangolli some forty years ago and are very useful for solving scattered data interpolation problems on the spaces. In the case the space is the $d$-dimensional unit sphere, J. Ziegel showed in 2013 that the radial part of a continuous positive definite and zonal kernel is continuously differentiable up to order $\lfloor...

Topics: Mathematics, Classical Analysis and ODEs

Source: http://arxiv.org/abs/1505.00029

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0.0

Jun 27, 2018
06/18

by
Fernando Barbosa V. da Silva; Fernando Albuquerque Oliveira; Marco AurÃ©lio A. Barbosa

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The thermodynamic and kinetics of the one dimensional lattice gas with repulsive interaction is investigated using transfer matrix technique and Monte Carlo simulations. This simple model is shown to exhibit waterlike anomalies in density, thermal expansion coefficient and self diffusion. An unified description for the thermodynamic anomalies in this model is achieved based on the ground state residual entropy which appears in the model due to mixing entropy in a ground state phase transition.

Topics: Condensed Matter, Soft Condensed Matter, Statistical Mechanics

Source: http://arxiv.org/abs/1503.03007

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Sep 23, 2013
09/13

by
Evy Salcedo; Ney Barraz; Marcia Barbosa

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Three core-softened families of potentials are checked for the presence of density and diffusion anomalies. These potentials exhibit a repulsive core with a softening region and at larger distances an attractive well. We found that the region in the pressure-temperature phase diagram in which the anomalies are present increases if the slope between the core-softened scale and the attractive part of the potential decreases. The anomalous region also increases if the range of the core-softened or...

Source: http://arxiv.org/abs/1212.6415v1

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Sep 21, 2013
09/13

by
Vera B. Henriques; Marcia C Barbosa

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We present a simple model for an associating liquid in which polymorphism and density anomaly are connected. Our model combines a two dimensional lattice gas with particles interacting through a soft core potential and orientational degrees of freedom represented through thermal \char`\"{}ice variables\char`\"{} . The competition between the directional attractive forces and the soft core potential leads to a phase diagram in which two liquid phases and a density anomaly are present....

Source: http://arxiv.org/abs/cond-mat/0407763v1

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Sep 18, 2013
09/13

by
Ricardo C. Correa; Valmir C. Barbosa

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Asynchronous executions of a distributed algorithm differ from each other due to the nondeterminism in the order in which the messages exchanged are handled. In many situations of interest, the asynchronous executions induced by restricting nondeterminism are more efficient, in an application-specific sense, than the others. In this work, we define partially ordered executions of a distributed algorithm as the executions satisfying some restricted orders of their actions in two different...

Source: http://arxiv.org/abs/cs/0611165v1

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Sep 18, 2013
09/13

by
A. H. L. Porto; V. C. Barbosa

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We introduce a new methodology for the determination of amino-acid substitution matrices for use in the alignment of proteins. The new methodology is based on a pre-existing set cover on the set of residues and on the undirected graph that describes residue exchangeability given the set cover. For fixed functional forms indicating how to obtain edge weights from the set cover and, after that, substitution-matrix elements from weighted distances on the graph, the resulting substitution matrix...

Source: http://arxiv.org/abs/q-bio/0504007v1

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Sep 22, 2013
09/13

by
V. C. Barbosa; L. C. D. Campos

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We introduce a novel evolutionary formulation of the problem of finding a maximum independent set of a graph. The new formulation is based on the relationship that exists between a graph's independence number and its acyclic orientations. It views such orientations as individuals and evolves them with the aid of evolutionary operators that are very heavily based on the structure of the graph and its acyclic orientations. The resulting heuristic has been tested on some of the Second DIMACS...

Source: http://arxiv.org/abs/cs/0309038v1

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Sep 22, 2013
09/13

by
V. C. Barbosa; R. G. Ferreira

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We study combinatorial indicators related to the characteristic phase transitions associated with coloring a graph optimally and finding a maximum independent set. In particular, we investigate the role of the acyclic orientations of the graph in the hardness of finding the graph's chromatic number and independence number. We provide empirical evidence that, along a sequence of increasingly denser random graphs, the fraction of acyclic orientations that are `shortest' peaks when the chromatic...

Source: http://arxiv.org/abs/cond-mat/0309518v1

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Sep 23, 2013
09/13

by
Paco Talero; Orlando Organista; Luis H. Barbosa

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The relation among instantaneous, mean and average velocities in one-dimensional motion with constant acceleration is studied. It was shown that the instant velocity evaluated in the time $t_{p}=\left(t_2+t_1\right)/2$ is similar to the mean and average velocities evaluated between the times $t_1$ and $t_2$. The reason for relations illustrated before were shown in detail. Also, the results obtained were used to propose a pedagogical strategy in order to study the one-dimensional motion with...

Source: http://arxiv.org/abs/1303.7025v1

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Sep 20, 2013
09/13

by
Ezequiel Barbosa; Luiz Gustavo Carneiro; Marcos Montenegro

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We introduce the notion of pseudohermitian k-curvature, which is a natural extension of the Webster scalar curvature, on an orientable manifold endowed with a strictly pseudoconvex pseudohermitian structure (referred here as a CR manifold) and raise the k-Yamabe problem on a compact CR manifold. When k=1, the problem was proposed and partially solved by Jerison and Lee for CR manifolds non-locally CR-equivalent to the CR sphere. For k > 1, the problem can be translated in terms of the study...

Source: http://arxiv.org/abs/1205.1840v1

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Sep 23, 2013
09/13

by
Marcelo R. Thielo; Marcia C. B. Barbosa

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We propose a model for a two dimensional, associative water-like lattice gas with one single variable representing both long and short-range interactions. The corresponding hamiltonian was solved exactly, by state enumeration in a finite lattice, so to obtain an analytic expression for the partition function. The lattice dimensions were chosen based on geometric characteristics of the stable phases found in previous works using Monte Carlo simulations. An expression for the particle density in...

Source: http://arxiv.org/abs/1111.4331v1

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Sep 22, 2013
09/13

by
Alan B. de Oliveira; Marcia C. Barbosa

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We study a very simple model of a short-range attraction and an outer shell repulsion as a test system for demixing phase transition and density anomaly. The phase-diagram is obtained by applying mean field analysis and Monte Carlo simulations to a two dimensional lattice gas with nearest-neighbors attraction and next-nearest-neighbors repulsion (the outer shell). Two liquid phases and density anomaly are found. The coexistence line between these two liquid phases meets a critical line between...

Source: http://arxiv.org/abs/cond-mat/0409138v1

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Sep 23, 2013
09/13

by
Fabio R. J. Vieira; Valmir C. Barbosa

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The field of algorithmic self-assembly is concerned with the design and analysis of self-assembly systems from a computational perspective, that is, from the perspective of mathematical problems whose study may give insight into the natural processes through which elementary objects self-assemble into more complex ones. One of the main problems of algorithmic self-assembly is the minimum tile set problem (MTSP), which asks for a collection of types of elementary objects (called tiles) to be...

Source: http://arxiv.org/abs/0710.0672v2

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Sep 22, 2013
09/13

by
L. M. A. Drummond; V. C. Barbosa

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Matrix clocks are a generalization of the notion of vector clocks that allows the local representation of causal precedence to reach into an asynchronous distributed computation's past with depth $x$, where $x\ge 1$ is an integer. Maintaining matrix clocks correctly in a system of $n$ nodes requires that everymessage be accompanied by $O(n^x)$ numbers, which reflects an exponential dependency of the complexity of matrix clocks upon the desired depth $x$. We introduce a novel type of matrix...

Source: http://arxiv.org/abs/cs/0309042v1

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27

Sep 22, 2013
09/13

by
L. D. Penso; V. C. Barbosa

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We consider a connected undirected graph $G(n,m)$ with $n$ nodes and $m$ edges. A $k$-dominating set $D$ in $G$ is a set of nodes having the property that every node in $G$ is at most $k$ edges away from at least one node in $D$. Finding a $k$-dominating set of minimum size is NP-hard. We give a new synchronous distributed algorithm to find a $k$-dominating set in $G$ of size no greater than $\lfloor n/(k+1)\rfloor$. Our algorithm requires $O(k\log^*n)$ time and $O(m\log k+n\log k\log^*n)$...

Source: http://arxiv.org/abs/cs/0309040v1

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62

Sep 17, 2013
09/13

by
Marco A. A. Barbosa; B. Widom

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We study the molecular correlations in a lattice model of a solution of a low-solubility solute, with emphasis on how the thermodynamics is reflected in the correlation functions. The model is treated in Bethe-Guggenheim approximation, which is exact on a Bethe lattice (Cayley tree). The solution properties are obtained in the limit of infinite dilution of the solute. With $h_{11}(r)$, $h_{12}(r)$, and $h_{22}(r)$ the three pair correlation functions as functions of the separation $r$...

Source: http://arxiv.org/abs/1003.2445v1

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37

Sep 19, 2013
09/13

by
Fabiano de S. Oliveira; Valmir C. Barbosa

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We revisit the deadlock-prevention problem by focusing on priority digraphs instead of the traditional wait-for digraphs. This has allowed us to formulate deadlock prevention in terms of prohibiting the occurrence of directed cycles even in the most general of wait models (the so-called AND-OR model, in which prohibiting wait-for directed cycles is generally overly restrictive). For a particular case in which the priority digraphs are somewhat simplified, we introduce a Las Vegas probabilistic...

Source: http://arxiv.org/abs/1010.4411v1